JVC VCR seems to constantly track (re-track) tapes?
 

Hello!

I have a JVC HR-S5902U that's been really good to me for the few years I've had it. Unfortunately it's begun giving me problems as of late :( The machine auto-tracks the tape while it plays (I don't even know if this thing will let me manually track!)...that has been a strong point of the machine up to this point. But lately, it seems like it's constantly tracking, and not accurately. I can put a pre-recorded VHS tape in that I know is in good shape, and it seems like it spends the entire duration of the tape moving briefly into the "sweet spot", moving out of the "sweet spot" until the picture's riddled with tracking lines/artifacts, then back into the "sweet spot". It didn't used to do this.

What does this symptom indicate? And, what can I do about it?

have you gave the deck a good manual cleaning with chamois and alcohol?
does the deck have alot of hours on it?

Indeed I did just give her a good cleaning yesterday. I started noticing this problem a few months back when I didn't have time to really deal with it, so I just put the machine away for the time being. I pulled it back out yesterday, gave it a good cleaning, then discovered the tracking issue I'd noticed before was still there.

As for hours, I haven't kept track. I'll say I've put MUCH less on this machine than I have machines in the past, but that doesn't really mean much, so....I guess the correct answer is "I don't know"?

Hi, and welcome.

The 5902 is actually one of the worst JVC unit, being a latter-generation 4600-4900, but with even cheaper parts inside. It was good for recording, but not playback. I used 3800s for years for recording, but palyback quality was blah. Better than a normal VHS VCR, yes, but not by much compared to JVC 7600+/9600+ units (or SR-V10/101).

It's not worth fixing if it has serious errors.

However, it sounds like typical JVC aging of the alignment. Every 2-3 year, most JVC decks a misaligned due to gravity. The positioning system isn't as exact as others. (This is a good thing, however, as it means you can purposely misalign JVC decks! Very useful for advanced restoration work.)

I've been using these decks for 15+ years now. Seen this over and over and over. Easy fix. :)

Thanks for the response :)

So what can I do? I'm not afraid to get my hands dirty, but is this something I can fix myself or is that not advisable?

This is not an issue with the tape path or any mechanical alignment, the VCR is constantly tracking in auto mode, going back and forth, and this can't be turned off anymore. I got one of these VCR (same model as OP) sitting in my e-lab right now, same issue.

According to the service manual, pressing the SP/EP button on the remote will stop auto tracking and you can use the Chan+ / Chan- buttons for manual tracking, but this doesn't work anymore. The on-screen display is supposed to show “AT: OFF” and that's not happening either.

Also, as long as you can't turn off auto tracking, you can't do any alignment changes to begin with. The oscilloscope and picture will be all over the place.

My best guess is a defective IC or EPROM, keeping the machine in permanent auto tracking mode, due to mixed up / false operational values / not being able to write read properly. The service manual doesn't offer any repair instructions for this.

The common cause to floating tracking is the lack of pulse signal coming from the stationary head that houses the linear audio track, the pulse track and their erase heads, The first step is to try to clean those stationary heads with a product that can dissolve dirt and grim but not damage plastics, Alcohol is a good candidate but sometimes is not strong enough, Use something pointy like cotton swab and make sure you get to the bottom edge of the pulse head. Next check the head connection, solder joints or ribbon cable mating surfaces on both the head itself and the main PCB, If a good connection is established by verifying the pulses are indeed reaching the PCB while playing a tape then it could be a faulty electronic component in the pulse head preamp, further diagnosis needed.

Mechanical components don't go out of alignment due to gravity, their own weight is not heavy enough to move them out of alignment. The possible causes of miss alignment are bad or damaged tapes, lack of maintenance (worn out components, dried up grease, deteriorated rubber...etc), miss handling and foreign objects, electronic failure causing mechanical failure and so many many more.

I cleaned all heads. Pulling the cable on the mono and tracking head caused the image to disappear, so some signal must be coming in.

When I play an EP tape, the playback speed is too fast, so the VCR is not adjusting accordingly. Do VCRs determine SP/EP through the tracking head and its routines?

I attached a short video. It loops through the same issue.

Yes, SP, EP and standard change for multi standard VCR's are determined by the pulse track frequency. Observe the tape passing the pinch roller and the stationary heads, Does it look stable and smooth with no curling or lifting?

Yes, that's all aligned properly. I adjusted it as well on all screws... the tracking issue never goes away.

I pulled the mechanics off the PCB. Don't see any hairline cracks, cold solder joints, leaked electrolyte, corroded traces, blown components, bulged caps. Only one IC has some color changes to it, maybe it got too hot. It sits in the system section, not A/V. If this thing is partly fried, it would explain why I can't disable auto tracking via remote. I attached a photo. The internals are all very clean.

I bought this thing for 30 bucks shipped on eBay. Seller said it runs for 10 sec and stops, so I assumed an easy fix. This is a different story and chasing this on the PCB without schematics / troubleshooting manual will be a pain in the ass.

Hooked up my oscilloscope and a multimeter. The audio head and the control head both get 2.3 V, the audio head produces a matching wave on the output, the control head only some high frequency noise, but no pulse.

Tried to find an audio control head combo for sale but there is nothing on eBay, not even for similar JVC VCRs.

What makes you think it's the head? What is the coil resistance of the pulse head? Compare it to another VCR you have, You can only rule the head being bad 100% if it has an open coil. If you hookup the pulse head to an audio preamp you should get a 50Hz (PAL/SECAM) or 60Hz (NTSC) tone.

Does linear (not hi-fi) audio sound normal? If it sounds muffled it could suggest the A/C head being out of alignment but if not it's probably not that.

Is there any pulses on the control track test point?

If it is indeed the head itself that's bad one option would be to salvage one from a different cheaper jvc with the same mechanism (they likely all used the same A/C head part).

Yes, mono audio is there and normal. Didn't find a control track test point. If there is one, I'd have to take off the mechanics and there is no way to connect the rotating head anymore.

The 2 heads / coils gives a signal / impulse directly on the small PCB that holds both heads. Audio wave is normal, matches the audio output, and shows on my oscilloscope, but the control head / coil is dead. It comes back at 300 ohms.

300 ohms is not dead, It is about right, OL or a reading of mega ohm could suggest an open coil.

Back to basics, clean the capstan and pinch roller.

If the tape slips you'll always be fighting the tracking.

It's not a guaranteed fix but it's essentially free and is routine service anyway.

I'm well past this, long done, its super clean and tape pull and alignment is not the issue.

The control head has no proper pulse while analog audio is spot on. There is no replacement part at this time on eBay. I have another JVC HR-S5901U incoming, yet another cheap eBay find for 30 bucks, but this one is supposed to be in working order. I'll swap the heads and report back.

On a side note, while this is a cheap late model S-VHS recorder, the image quality is extremely good (when the auto tracking hits the sweet spot for a couple seconds). I think it is the best recorder with S-video out an an extreme budget.

I'm afraid that this is not going to be a head issue, your impedance reading of the head coil seem to be pretty normal, this is most likely a head preamp issue or something else.